Suspected Boko Haram militants killed at least 10 villagers in northern Cameroon on Sunday night in what army and local officials said was revenge for attacks by Cameroon’s army.

Cameroon’s semi-arid far North region has been a target of Boko Haram suicide bombings and raids for eight years as the Islamist insurgency spilled over the border from Nigeria, killing 20,000 and uprooting nearly three million in the Lake Chad region.

Cameroon forces have tried to beat back insurgents but have struggled to stop unpredictable attacks that have been the hallmark of Boko Haram’s bid to carve out an Islamic state.

A senior army source said the attackers came to the village of Gouderi at 11 pm on Sunday and killed 11 people.

Two local officials told Reuters by phone that “about 10” had been killed.

“It looks like revenge because the army killed Boko Haram members in this village and forced others to retreat to Nigeria,” the army source said.